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>Drag-and-drop (DND)</H1
><P
>GTK+ has a high level set of functions for doing inter-process
communication via the drag-and-drop system. GTK+ can perform
drag-and-drop on top of the low level Xdnd and Motif drag-and-drop
protocols.</P
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>Overview</A
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><P
>An application capable of GTK+ drag-and-drop first defines and sets up
the GTK+ widget(s) for drag-and-drop. Each widget can be a source
and/or destination for drag-and-drop. Note that these GTK+ widgets must have
an associated X Window, check using GTK_WIDGET_NO_WINDOW(widget)).</P
><P
>Source widgets can send out drag data, thus allowing the user to drag
things off of them, while destination widgets can receive drag data.
Drag-and-drop destinations can limit who they accept drag data from,
e.g. the same application or any application (including itself).</P
><P
>Sending and receiving drop data makes use of GTK+ signals.
Dropping an item to a destination widget requires both a data
request (for the source widget) and data received signal handler (for
the target widget). Additional signal handers can be connected if you
want to know when a drag begins (at the very instant it starts), to
when a drop is made, and when the entire drag-and-drop procedure has
ended (successfully or not).</P
><P
>Your application will need to provide data for source widgets when
requested, that involves having a drag data request signal handler. For
destination widgets they will need a drop data received signal
handler. </P
><P
>So a typical drag-and-drop cycle would look as follows:</P
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> Drag begins.</P
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> Drag data request (when a drop occurs).</P
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><LI
><P
> Drop data received (may be on same or different
application).</P
></LI
><LI
><P
> Drag data delete (if the drag was a move).</P
></LI
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> Drag-and-drop procedure done.</P
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>There are a few minor steps that go in between here and there, but we
will get into detail about that later.</P
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